Very useful info Tom. I've been looking for some sort macro lens adapter for my RX100. Looks like this ring along with a Raynox DCR-150 or 250 might be what I need.

Are you familiar with the Raynox 150/250? And if so, any preference between the two and why?

Unfortunately, no -- I'm not familiar with either of them. I think they've been used by plenty of folks on other Sony cameras, though -- if you post a new thread asking about them, I'm sure you'll get replies from folks who are very familiar with them.